import java.util.Scanner;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: Admin
 * Date: 2022-12-03
 * Time: 17:06
 */
public class Demo1 {
    public static void main(String[] args) {
        long[] d = new long[21];
        d[0] = 0; d[1] = 0; d[2] = 1;
        //0个人的时候不出会出错,概率为0,
        //1一个的时候也不会出错,概率为0,
        //2个人的时候有1种出错方式,概率为50%.

        long[] f = new long[21];
        f[0] = 1; f[1] = 1; f[2] = 2;
        //0的阶乘为1,1的阶乘也是1,2的阶乘为2;

        for(int i = 3; i < 21; i++) {
            d[i] = (i - 1) * (d[i-1] + d[i-2]);
            f[i] = f[i - 1] * i;
        }

        Scanner scan = new Scanner(System.in);
        while(scan.hasNextInt()) {

            int n =scan.nextInt();
            System.out.printf("%.2f%%\n",100.0 * d[n] / f[n] );
        }
    }
}
